Terraform autoscaling group example

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Terraform autoscaling group example

As part of the lead up to the release of Terraform 0. A common problem in Terraform configurations for versions 0. The general problem of iteration is a big one to solve and Terraform 0.

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We also discuss further enhancements that will come later. When working with lists and maps, it is common to need to apply a filter or transformation to each element in the collection and produce a new collection. Prior to Terraform 0.

Terraform 0. The example below shows this in use:. When a for expression is wrapped in square brackets [ and ] as shown above, the result is a list. For example:. The optional if clause can be used also to filter the input collection so that the result contains only a subset of input items:. Finally, the map form of a for expression has a grouping mode where the map key is used to group items together into a list for each distinct key.

This mode is activated by placing an ellipsis These new expressions can be used to generate a value for any argument that expects a list or map expression.

And in Terraform 0. Several resource types use nested configuration blocks to define repeatable portions of their configuration. The example below shows the Terraform 0. Because these nested blocks are validated statically, it was previously difficult or impossible to implement more dynamic behaviors.

Some users found ways to exploit some implementation details to trick Terraform into partially supporting dynamic generation of blocks, but these workarounds were unreliable because Terraform makes assumptions about nested blocks that do not hold for arbitrary expressions.

The same example converted to Terraform 0. Because dynamic is itself given as a nested block, all of the same syntax constructs can be used within its content block that would normally be valid in a literal tag block, and both static and dynamic tag blocks can be mixed as shown above.

This enables arbitrarily complex behaviors as necessary.

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Thus this approach allows more problems to be caught at plan time, before any real actions have been taken. We still recommend that you avoid writing overly-abstract, dynamic configurations as a general rule. These dynamic features can be useful when creating reusable modules, but over-use of dynamic behavior will hurt readability and maintainability.Comment 2. The idea is that you give them a desired capacity, and the knowledge of how to launch more machines, and they will fully automate spinning your fleet up and down as the desired capacity changes.

We must wait for all builds to finish before we can terminate an instance. But, it is a problem that gets solved differently depending on the size of your fleet and your usage pattern. For example, we use a custom system to scale our CircleCI. At a high level, our solution includes four parts:. We use Terraform for managing our CircleCI. The resources that follow will be listed as terraform examples, but the approach will still work if you want to build it manually or by using CloudFormation.

Rather than automating our manual scaling strategies for CircleCI Enterprise customers, we wanted to provide hooks into existing best practices. ASGs provide a lot of flexibility. In their simplest form, they act as very basic fault tolerance, automatically spinning up new machines if any of the machines stop working. For us, our graceful shutdown must wait for builds to finish before it can terminate an instance, a process which can take half an hour or more.

Rather than writing our own endpoint, we decided to let Amazon handle maintaining the state of which instances need to be terminated for us.

Using a queue here was the right solution for us because our master can shut down any of its slaves, thus we only have a single consumer. The only part left is the actual consumption from the queue, and the graceful shutdown of the machine. First, Amazon sends a test notification when you first attach a Lifecycle Hook to make sure the connection works properly:. How you consume these notifications is entirely up to you. In our case, we just added a bash script wrapped inside a Docker container that our customers can install on our main master machine.

We did it this way because we wanted to give our customers something pre-packaged, and easy to install on the machine. Auto Scaling groups have long been a great choice for managing scaling, because they offer such flexibility in how you scale.There's a common misconception that autoscaling means automatic scaling up or scaling down. But in most cases, it actually means metrics-based scaling. However, Joyent used HashiCorp Nomad to build true autoscaling that works for any cloud.

Learn more in this blog post. The concept of autoscaling for the cloud can be as simple as a distributed cron job. If you use a cloud, or a private virtualisation environment that doesn't support autoscaling, then you can use HashiCorp Nomad to build your own.

terraform autoscaling group example

In this session, Paul Stack, a software developer at Joyent, demonstrates how he used Nomad to build an autoscaling feature on top of Joyent's Triton cloud. Okay, so my name's Paul Stack, I work for a company called Joyent, and I'm here to talk about how to build your own autoscaling feature using Nomad. Everybody know what Nomad is I'm presuming?

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Someone not know what Nomad is? Okay, so we'll look at it as we go through. Autoscaling is supposedly a very simple concept that allows you to scale up or scale down a system in a simple manner, that allows you to optimize for cost. For example, every day in your development environment or your test environment, you can actually spin your entire environment up during the work hours, and only be paying for that time, and then at the end of the day, spin it back down so that you're not actually wasting money.

Autoscaling, it's an interesting name for the concept. A lot of major clouds have it, so Amazon has it. This is all Terraform configuration codes []so if it looks a little alien, I apologize.

I primarily use that Terraform code.

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In Amazon, you basically pass a name of an Auto Scaling group "Auto Scaling" is the AWS-specific product nameyou pass the max size, the min size, and then the desired capacity of how many instances you want running. You can give it a specific health check and you can launch it based off a known configuration. It's quite a simple way, but you actually have constraints about how many it's allowed to run to, and the minimum that it's allowed to.

Azure has a very similar concept. They have something called scale sets, and the Terraform configuration is slightly more long-winded in this case, only because it's a different configuration.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. This project is part of our comprehensive "SweetOps" approach towards DevOps. We literally have hundreds of terraform modules that are Open Source and well-maintained.

Check them out! In your code, do not pin to master because there may be breaking changes between releases. Instead pin to the release tag e. Like this project? Are you using this project or any of our other projects? Consider leaving a testimonial. File a GitHub issuesend us an email or join our Slack Community.

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AWS/Terraform Workshop #2: EC2 Networking, Autoscaling Groups, CloudWatch

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Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. HCL Makefile Go. HCL Check out introductory workshop and new posts at Smartling Engineering Blog. Each region is a separate geographic area that has multiple, isolated locations known as Availability Zones.

Amazon EC2 provides you the ability to place resources, such as EC2 instances and data in multiple locations. Amazon data centers provide high speed connections between AZs but you should keep in mind that usually inter-AZ communications adds about 1 ms latency in comparison to communications within the same AZ.

At the same time the possibility to make changes into AWS networking configuration is open to service owners. Each subnet resides within one AZ and cannot span zones. There are public and private subnets. Private subnets are used for those resources which should not be exposed to Internet. Most of our SOA components reside in private subnets for security reasons.

EC2 security group acts as a virtual firewall that controls the traffic for one or more EC2 instances. When you launch an instance, you associate one or more security groups with the instance. You can add rules to each security group that allow traffic to or from its associated instances.

You can modify the rules for a security group at any time — the new rules are automatically applied to all instances that are associated with the security group. You can use CloudWatch to collect and track metricswhich are the variables you want to measure for your resources and applications like CPU load, network traffic IO etc.

CloudWatch alarms send notifications or automatically make changes to the resources you are monitoring based on rules that you define, for example trigger Autoscaling Group to scale. A metric is the fundamental concept in CloudWatch. It represents a time-ordered set of data points that are published to CloudWatch. These data points can be either your custom metrics or metrics from services in AWS.

You can retrieve statistics about those data points as an ordered set of time-series data. Think of a metric as a variable to monitor, and the data points represent the values of that variable over time. CloudWatch namespaces are containers for metrics. Metrics in different namespaces are isolated from each other, so that metrics from different applications are not mistakenly aggregated into the same statistics.

Every metric has specific characteristics that describe it, and you can think of dimensions as categories for those characteristics. Dimensions help you design a structure for your statistics plan. Cloudwatch alarm watches a single metric over a time period you specify, and performs one or more actions based on the value of the metric relative to a given threshold over a number of time periods. CloudWatch alarms will not invoke actions simply because they are in a particular state, the state must have changed and been maintained for a specified number of periods.

Auto-scaling with AWS and terraform

After an alarm invokes an action due to a change in state, its subsequent behavior depends on the type of action that you have associated with the alarm. For Auto Scaling policy notifications, the alarm continues to invoke the action for every period that the alarm remains in the new state. An alarm has three possible states :. Auto Scaling helps you ensure that you have the correct number of EC2 instances available to handle the load for your application.

terraform autoscaling group example

The same with maximum number of instances. If you specify desired capacityeither when you create the group or at any time thereafter, ASG ensures that your group has this many instances.

When you create a launch configuration, you specify information for the instances such as the ID of the Amazon Machine Image AMIthe instance type, security groups etc.

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Auto Scaling provides several ways for you to scale your ASG :.This is Part 5 of the Comprehensive Guide to Terraform series. In previous parts, we explained why we picked Terraformintroduced the basic syntax and features of Terraformdiscussed how to manage Terraform stateand showed how to create reusable infrastructure with Terraform modules. Terraform is a declarative language.

However, without access to a full programming language, certain types of tasks become more difficult in a declarative language. Note that all the code samples are written for Terraform 0. Terraform offers several different looping constructs, each intended to be used in a slightly different scenario:. Now that you have this user, you can create and manage all future IAM users with Terraform.

Consider the following Terraform code:. What if you wanted to create three IAM users? Terraform does not have for-loops or other traditional procedural logic built into the language, so this syntax will not work. However, every Terraform resource has a meta-parameter you can use called count. Therefore, you can create three IAM users as follows:.

terraform autoscaling group example

One problem with this code is that all three IAM users would have the same name, which would cause an error, since usernames must be unique. If you had access to a standard for-loop, you might use the index in the for loop, ito give each user a unique name:.

To accomplish the same thing in Terraform, you can use count. If you combine count. If you were using a general-purpose programming language with loops and arrays, you would configure each IAM user to use a different name by looking up index i in the array var.

In Terraform, you can accomplish the same thing by using count plus two new tricks. The first trick is to use array lookup syntax to look up elements in an array at a given index. This syntax is identical to what you see in most other programming languages:. As you can probably guess, the length function returns the number of items in the given LIST. It also works with strings and maps.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. The ASG stays unaffected. How do I recreate now the instances in that ASG i.

What I've tried: With terraform taint one can mark resources to be destroyed and recreated during the next apply. However, I don't want to taint the autoscaling group which is a resource, and single instances are not in this casebut single instances in it. Is there a way to taint single instances or am I thinking in the wrong direction?

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The normal thing to do here is to use Terraform's lifecycle management to force it to create new resources before destroying the old ones.

In this case you might set your launch configuration and autoscaling group up something like this:. This will flip all the instances in the ASG at once. So if you had a minimum capacity of 2 in the ASG then this will create 2 more instances and as soon as both of those pass health checks then the 2 older instances will be destroyed.

In the event you are using an ELB with the ASG then it will join the 2 new instances to the ELB so, temporarily, you will have all 4 instances in service before then destroying the older 2.

You cannot solve this with terraform alone. When you change the launch configuration for your Auto Scaling group, any new instances are launched using the new configuration parameters, but existing instances are not affected. This isn't an answer per se, but I struggled with this as well.

Tagging Auto Scaling Groups and Instances

In one context it was general, in another, Kubernetes. I ended up writing an open-source service to watch and auto-rolling update. Learn more. How to recreate EC2 instances of an autoscaling group with terraform? Ask Question.

terraform autoscaling group example

Asked 3 years, 7 months ago. Active 1 year, 1 month ago. Viewed 5k times. Why do you want the ASG to stay unaffected? The normal use case in this situation is to rolling replace the ASG and the instances inside it.

It's confusing that I talked about a single instance, so I update the question. Active Oldest Votes. GabLeRoux I had min, max, and desired capacity set all to 1 before.

I changed this now to 1, 2, and 1 based on your answer.


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